Deflecting coil for cathode ray tubes



FIN/5H 2 Sheets-Sheet 2 I FIN/J ll HOE/Z WINDING I w. A. TOLSON in" ALDEFLECTING COIL FOR CATHODE RAY TUBES Filed Nov. :50, 19:55

50b 61b 6'21) 40a 41a 42a. 60a, 61a 52a 40b 41b 42115011516 April 25,1939.

VENT/GIL WINDING 3 INVENTOHJ Vl illiam A. Tol-son/ H'I'TOHNEY Ioury G.Mal off .1:

Patented Apr. 25, 1939 UNITED STATES PATENT OFFICE DEFLECTING COIL FORCATHODE RAY TUBES aware Application November 30, 1935, Serial No. 52,318

11 Claims.

Our invention relates to cathode ray deflecting devices and particularlyto deflecting devices of the electromagnetic type.

Progressive advancements in the art of television have imposed ratherstringent requirements upon deflecting devices and deflecting circuitsused for deflecting a cathode ray beam at both the televisiontransmitter and the television receiver as regards linearity ofdeflection, em-

ciency of the deflecting devices and circuits, and defocusing of theelectron beam. Deflecting coils have certain advantages overelectrostatic defleeting plates, one advantage being that it permits acheaper cathode ray tube construction since the cost of addingdeflecting plates'to the tube is avoided. However, considerabledifficulty was encountered in designing an electro-magnetic deflectingdevice which was eflicient and which i did not defocus the electron beama considerable amount. It was finally discovered that the major portionof the defocusing of the electron beam was caused by the non-uniformflux distribution in the plane perpendicular to the electron beam. 28 Anobject of our-invention is to provide an improved deflecting device fora cathode ray tube. A further object of our invention is to provide adeflecting device which causes minimum defocusing of the electron beam.30 A further object of our invention is to provide improved deflectingcoils for a cathode ray tube. A still further object of our invention isto pro-- vide improved deflecting coils which produce a magnetic fleldhaving substantially uniform flux distribution in a plane perpendicularto the cathode ray.

In practicing our invention, we employ a distributed form of winding forthe deflecting coils.

- In one embodiment of the invention, a laminated 40 iron core or yokeis employed, the core having slots therein in which the coils of thewinding are placed. The distributed winding may be applied to the yokeby methods commonly employed in winding motors, but, as will beexplained later, it is generally preferred to have the winding skip aslot, that is, have it non-uniformly distributed, in order to obtain amore uniform flux distribution.

Other objects, features and advantages of our invention will appear fromthe following description in which Figure 1 is a side view of a cathoderay tube having mounted thereon a set of deflecting coils 5 constructedin accordance with our invention;

Fig. 2 is an end view on an enlarged scale of the deflecting coils shownin Fig. 1;

Fig. 3 is a winding diagram of the deflecting coils shown in Fig. 2;

Fig. 4 is an end view of a set of deflecting co 5 wound in accordancewith another embodiment of our invention;

Fig. 5 is a winding diagram of the deflecting coils shown in Fig. 4;

Fig. 6 is both a diagram of the flux distribution 10 mounted on acathode ray tube of well known 20 design. The cathode ray tube comprisesa highly evacuated envelope 60 having therein an electron gun 6! whichincludes a first anode 62. A second anode 63 is provided, which'consistsof a metallic coating on the inner surface of the en- 25 -velope 60. Thecathode ray. indicated by the dash-dot line 64, is focusedelectro-statically by means of the electro-static fleld between thefirst and second anodes. The electro-static focusing causes the electronbeam to be concentrated to 30 a beam of very small diameter at thefluorescent screen 65 located at the end of the cathode ray tube. Aspreviously stated, it is one of the objects of our invention to providedeflecting coils which do not disturb this focusing of the electronbeam. 35 It will be understood that magnetic focusing may be substitutedfor the electro-static focusing.

Referring to Figs. 1 and 2, a laminated iron core or yoke 66 isprovided, each lamination being a thin sheet of soft iron and having aplurality of slots cut therein. These laminations are stacked to form acore having a plurality of longitudinal slots therein which extendparallel to the longitudinal axis of the cathode ray tube.

In the specific embodiment being described, the 5 core has twelve slotswhich are indicated by the reference numerals I to I2. It will beunderstood that a more uniform magnetic fleld may be obtained byemploying more slots with a corresponding increase in the number ofcoils. In Fig. 2, there are illustrated both a horizontal deflectingwinding and a vertical deflecting winding, the horizontal deflectingwinding consisting of coils 20a, Ila and no on the top side of the core66 and the coils 26b, 2| b and 22b on the bottom side of the core. Thevertical deflecting windings consist of the coils a, Ila and 324 on theright hand side of the core and the coils 80b, lib and 32b on the lefthand side of the core. In Fig. 1, only the ends of the coil 32a can beseen.

The winding shown in Fig. 2. and more clearly shown in Fig. 3, is of theconcentric coll type. Referring to the horizontal winding, it will benoted that there is no horizontal winding condoctor in the slots 4 andIt. The conductors of the coil 20a are located in slots 3 and I, theslot 4 being skipped. The conductors of the coil Zia are in slots 2 andi, and the conductors of the coil 22a are in the slots l and 1. It willbe noted that the three coils 200, Ma and 221; are located symmetricallywith respect to the slot 4. Each coil preferably includes a plurality ofturns, the number of turns depending upon the character of the circuitsupplying the defleeting current and upon the frequency of occurrence ofthe deflecting cycle.

Referring to the lower portion of the horizontal deflecting winding, theconductors of the coil 20b are located in slots 9 and ii, the slot Illbeing skipped. The conductors of the coil 2Ib are located in slots 8 andI! while the conductors of the coil 22b are located in slots 1 and i. Itwill be understood that the lower portion of the horizontal deflectingwinding is a, duplicate of the upper portion, the coils 20a and 20bcontaining the same number of turns, and, similarly, the coils 2m and 2|b containing the same number of turns. In the speciflc example heredescribed, all the coils contain the same number of turns, anywhere fromten to several hundred, depending upon operating conditions, but itshould be understood that in some instances the uniformity of fluxdistribution may be improved by having a diflerent number of turns inone coil than in another. For example, the coil 20a might have fiftyturns and the coil 22a flfty-flve turns.

The way in which the coils are connected is shown in Fig. 3 where thehorizontal deflecting winding is represented by the light lines and thevertical deflecting winding by the heavy lines. The winding diagram inFig. 3 is in the form of a conventional motor winding diagram, it beingassumed that the core and windings have been cut at the slot l2 and thenflattened out. In order to simplify the diagram, only one turn per coilis shown. In Figs. 2 and 3, like parts are indicated by the samereference characters.

The vertical deflecting winding is the same, except, perhaps, for thenumber of turns per coil, as the horizontal deflecting winding and islocated at right angles to it. On the right hand side,.the conductors ofthe coil 30a are located in the slots 6 and 1, the slot 1 being skipped.The conductors of the coil lla are located in the slots 5 and 9, whilethe conductors of the coil 32a are located in the slots 4 and ill.

On the left hand side, the conductors of the coil 30b are located in theslots 2 and II, the slot I being skipped. The conductors of the coil Slbare located in the slots 3 and II and the conductors of the coil 32b arelocated in the slots 4 and Ill.

The way in which the coils of the vertical deflecting winding areconnected is shown in Fig. 3, where the ends of the conductors which areconnected together are indicated by like reference characters.

Instead of employing the concentric coll winding described above, thedeflecting coils may belap wound, as shown in Figs. 4 and 5. In thestructure shown in these figures, the horizontal deflecting winding andthe vertical deflecting winding are wound on a core similar to the onedescribed above. The horizontal deflecting winding consists of the coils40a, Ma and 42a at the top of the core and the coils 4.1:, Nb and 42b atthe bottom of the core. The conductors of the coil a are located inslots 1 and I, the conductors of coil 4ia are located in slots 2 and Iand the conductors of 42s are located in slots 3 and I. It will beapparent from the drawings that in slot 4 there are no conductors of thehorizontal deflecting coils and that these coils are locatedsymmetrically with respect to the slot 4. Likewise, the lower coils 40b,4lb and 425 are located symmetrically about the slot I I which has nohorizontal deflecting coil conductors located therein.

The winding diagram in Fig. 5 shows how the coils are connected, likeparts in Figures 4 and 5 being indicated by the same referencecharacters. The ends of the windings which are connected together areindicated by the same reference characters in Fig. 5.

The vertical deflecting winding consists of the coils 500, Sin, and "aon the right handside of the core and'the coils 50b, Slb and 52b on theleft hand side of the core. It will be evident upon inspection of Fig. 4that the coils on the right hand side of the core skip the slot 1 whilethe coils on the left hand side of the core skip the slot I.

In Fig. 4, the connections for the vertical deflecting coils areindicated by the winding in heavy lines. The ends of the windings whichare'to be connected together are indicated by the same referencecharacters; For example, the conductor end marked at the right hand sideof Fig. connects to the conductor end marked c at the left hand side ofFig. 5.

Instead of employing laminations having open slots, as shown in Figs. 2and 3, laminations having slots which are partially closed, as shown inFig. 6,.may be employed. In some instances, this may aid in obtaining amore uniformly distributed flux.

Either of the distributed windings described above will produce amagnetic fleld which is substantially uniform in a plane at right anglesto the longitudinal axis of the cathode ray tube,

that is, in the plane of the paper in Figs. 2 and 3. 'As a result. thedeflecting coils do not disturb the focusing of the electron beam andthe Y In Fig. 6 the flgures indicate the flux distribution in a planetaken through the center of the deflecting yoke or core 6, this planebeing at right angles to the axis of the electron gun. The amount offlux is indicated in arbitrary units, each point at which a measurementwas taken being marked by an x. The dotted rectangle ll indicates theregion through which the cathode ray is deflected. In this region thevariation in the amount of flux at different points does not exceed 5%of the minimum value.

It has been found that if the flux variation is of the order of 5% orless in a plane at right anglm to the beam, as shown in Fig. 6, thedefocusing of the beam is so slight that a very high quality picture maybe obtained. Even if the value of the flux varies as much as 10%, therewill be only a small amount of defocusing of the beam as compared withthat produced by conventional deflecting coils.

In Fig. 7 the dotted circle Ii represents the inner periphery of thecore 66 and the dotted rectangle 12 represents the region through whichthe cathode ray is deflected. The flgures next to each point marked byan a: show the flux distribution for uniformly distributed windings.That is, this flux diagram shows the flux distribution of deflectingcoils wound as shown in either Fig. 2 or Fig. 4 without skipping a slot.It will be noted that the flux varies from the value 44 in the center tothe value 30 next to the inner periphery of the core. A variation ofthis magnitude will cause serious defocusing.

The flux diagrams in Figs. 6 and 7 are for the horizontal deflectingwindings only which produce a" flux in the direction from the top to thebottom of the drawings, as indicated by the letters ings which aredistributed. Also,- a fairly uniform flux distribution may be obtainedby resorting to expedients other than that of distributing the windings.

From the foregoing description, it will be apparent that variousmodifications may be made in our invention, without departing from thespirit and scope thereof and we desire, therefore, that only suchlimitations shall be imposed thereon as are necessitated by the priorart and as set forth in the appended claims.

We claim as our invention:

1. In combination with a cathode ray tube, electro-magnetic deflectingmeans, said means comprising a pair of diametrically opposed distributedwindings which are concentrically wound.

2. In combination with a cathode ray tube having an electron gun,electro-magnetic deflecting means, said means comprising a pair ofdiametrically opposed distributed windings which are so distributed thattheir magnetic fleld is substantially uniform in a plane at right anglesto the axis of said gun whereby defocusing of the oathode ray isminimized.

3. The invention according to claim 2, char acterised in that the saidwindings are concentrically wound.

4. The invention according to claim 2, characterised in that the saidwindings are lap wound.

5. In combination with a cathode ray tube having an electron gun, meansincluding deflecting coils comprising distributed windings which are sodistributed as to produce a magnetic deflecting field which, from pointto point in a plane at right anglestotheaxisofsaidgunandintheregionthrough which the cathode ray is deflected, does not vary in value morethan of the minimum value.

6. In combination with a cathode ray tube having an electron gun, meanscomprising diametrically opposed distributed windings which are sodistributed as to produce a magnetic deflecting field which, from pointto point in a plane at right angles to the axis of said gun and in theregion through which the cathode ray is deflected, does not vary invalue more than 10% of the minimum value.

'7. In combination with a cathode ray tube, electro-magnetic deflectingmeans, said means comprising a pair of non-uniformly distributedwindings, each winding consisting of a plurality of coils, and each coilhaving a plurality of turns, certain coils having a different number ofturns than other coils.

8. In combination with a cathode ray tube, a pair of deflecting coils,supporting means for said coils, said supporting means having an openingtherein through which a portion of said tube may be passed, one coil ofsaid pair comprising a plurality of distributed windings which aredistributed about said supporting means on one side of said opening andthe other coil of said pair also comprising a plurality of distributedwindings which are distributed about the opposite side of saidsupporting means.

9. In combination, a cathode ray tube having therein means for producingan electron beam, and deflecting means for deflecting said electronbeam, said deflecting means comprising a pair of diametrically opposeddistributed windings.

10. In combination with a cathode ray tube, a deflecting yoke comprisinga pair of deflecting coils, supporting means for said coils, saidsupporting means having an opening therein through which a portion of acathode ray tube may be passed, one coil of said pair comprising aplurality of distributed windings which are distributed about saidsupporting means on one side of said opening and the other coil of saidpair also comprising a plurality of distributed windings which aredistributed about said supporting means on the opposite side of saidopening, said windings being so distributed that in a plane at rightangles to the longitudinal axis of said opening and within said openingtheir magnetic fleld is approximately uniform whereby defocusing of acathode ray during deflection is minimised.

11. In combination with a cathode ray tube, a deflecting yoke comprisingtwo pairs of deflecting coils, one of said pairs comprising twodiametrically opposed distributed windings and the other of said pairscomprising two diametrically Opposed distributed windings located atright angles to said flrst pair whereby the flelds of said two pairs ofcoils are substantially at right angles to each other.

WILLIAM A. 101.808. IOURY G. MALOI'I'.

